That works until you have a verb which can be either transitive or intransitive, and may or may not take the dative.
Which is what ambitransitivity means. The verb can only be one in a given sentence, there's no way a verb phrase could contain a verb that is both transitive and intransitive at the same time (unless we want to get invent some form of quantum linguistics but somehow I doubt that would work very well), the verb would be ambitransitive and, in a given context, one or the other.
The way I think about it is this.
- If the verb is transitive then the DirObj of the causative remains the original DirObj, and receives the ACC.
Oel taron yertikit. —› Oel teykaron yerikit [fa ’awpo/’awpor.]
- If the verb is (strictly) intransitive then there's no DirObj, as the only Arg is the Subj. The original Subj becomes the causative DirObj, and receives the ACC.
Tìrusol sngä’i. —› Oel sngeykä’i tìrusolit [fa ’awpo/’awpor.]
- If the verbs takes a dative Obj (like some si compounds) then ‹eyk› turns the verb into a standard transitive one, and it behaves accordingly (see #1.)
Oe uvan si uvanur. —› Oel uvan seyki uvanit [fa ’awpo/’awpor.]
Perhaps I'm missing something, but I see nothing confusing about this. Regardless of your original verb, the causative syntax is always the same. I think your mistake is that you try to understand the workings of the causative construct from the perspective of the original verb – which is no longer there.
In your second example, I don't think you could have the dative intermediate causer there because then you'd effectively have a doubly causative verb and that would be a pain to do and might require an additional <eyk> infix.
Anyway, you describe situations of transitives which become ditransitive with the causee becoming dative, intransitives which become transitive and dative transitives which become ditransitive with the causee becoming accusative; the problem is this argument is about none of those, but whether ambitransitives behave as whichever they are used as most commonly or whether they behave as they are being used in the sentence.
So, whether oe taron counts as a transitive for the purposes of your causative algorithm, or whether it counts as an intransitive. It is sadly a grey area.